JPH03204592A - Heat exchanger - Google Patents

Abstract

PURPOSE:To reduce pressure loss and increase heat transfer efficiency by a method wherein an spiral element is constituted of a plurality of unit elements having a specified twisting angle and connected continuously with a specified connecting angle while the twisting directions of neighboring unit elements are designed so as to be reversed. CONSTITUTION:A spiral element 1 is constituted of a plurality of unit elements 1a,... having a twisting angle 180 deg. while the twisting direction is reversed in every unit element and the unit elements are connected with a connecting angle 0 deg.. Therefore, the spiral element 1 exists as a continued one spiral sheet extending lengthwise in a tube. Accordingly, the spiral element 1 divides the tube into two channels when the same element 1 is arranged in the tube. When heat exchanging liquid flows into a heat exchanger A equipped with four pieces of inner tubes 2,..., for example, the tube is divided into two channels whereby divided liquid moves lengthwise in respective channels while effecting spiral motions in respective unit elements 1a,... in respective channels and being twisted into reverse directions in every unit element 1a.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is a heat exchanger that is composed of an inner and outer tube with a spiral body inside the inner tube, and that exchanges heat of a fluid (particularly a liquid) between the inner tube and the outer tube. Concerning vessels.

[Prior Art and Problems] Some conventional heat exchangers are equipped with a large number of heat transfer fins and baffle plates in order to improve heat exchange efficiency. However, in this type of heat exchanger, a so-called channeling phenomenon occurs in which the fluid flows in a layered manner, and there is a limit in terms of improving heat exchange.

In addition, a 90° baffle plate with a 180° twist is installed inside the inner tube.
``Connections are made alternately in opposite directions with connection angles. A so-called static mixer is also used. However, in this case, the structure is extremely complicated due to the large number of connection parts, and it requires a large amount of man-hours in manufacturing. Therefore, this problem is particularly problematic when it is necessary to install a large number of inner pipes or use long and large pipes to secure a large heat transfer area.Furthermore, the pressure loss is large, and from the standpoint of energy saving, There are also challenges.

[Solution Means and Effects] Therefore, the present invention employs the following means in order to have heat transfer characteristics equivalent to those of a conventional heat exchanger using a static mixer and to solve the above problems.

Includes a helical element extending longitudinally within the tube.

The helical element consists of a plurality of unit elements each having a twist angle of 180° and connected at a connection angle O0.

Adjacent unit elements are twisted in opposite directions.

A heat exchange tube body characterized by:

If this heat exchange tube body is used as an inner tube and one or more inner tubes are disposed within the outer tube with a gap, the main part of the heat exchanger is constituted.

According to such means, the structure is extremely simpler than that using a static mixer, and, as will be made clear from the test results of the examples described later, it is possible to achieve the same heat transfer effect.

In addition, since the pressure loss is extremely low, it is preferable from the viewpoint of energy saving, and this effect is particularly noticeable in heat exchangers such as long and large pipes, and with low viscosity liquids, and has a great practical advantage.

[Preferred Means] The heat exchange medium is effective for liquids, especially low viscosity liquids with Re > 104, such as water. Difficulties during heat exchange (channeling phenomenon) peculiar to liquids also hardly occur.

The helical element is preferably joined to the inner wall of the pipe by brazing. It can be easily joined and high heat transfer efficiency can be ensured. Furthermore, this joining also serves to reinforce the inner tube, and even if its wall thickness is made thinner, there is less deflection, which contributes to increasing the heat transfer efficiency of the tube.

The spiral element described above provides the effect of reverse torsional agitation, and does not necessarily require baffles in the gaps between the inner and outer tubes.

The number of unit elements constituting the spiral element - is appropriately selected depending on the application. In addition, the spiral element is welded after manufacturing the unit element.

It can be soldered or manufactured as one piece from the beginning.

In addition, the ratio (1-, / D
) is preferably about 1 to 3, similar to the unit element of a normal static mixer.

[Example] FIG. 1A shows a helical element 1 according to this example, and the helical element 1 has a plurality of twist angles of 180° (4 in the figure).
), each unit element is twisted in the opposite direction and connected at a connection angle O0. Therefore.

The helical element 1 is present in the tube as a continuous helical sheet extending longitudinally. In this respect, the elements of a typical conventional static mixer are completely different from the structure (FIG. 1B) in which unit elements are discontinuously connected to each other at a connection angle (for example, 90 degrees).

Thus, when the helical element 1 of one example (invention) is deployed in a pipe, it only divides the pipe into two channels.

The spiral element 1 (unit element 1a...) is
Depending on the type and pressure of the liquid flowing inside the inner tube, it is preferable to use a material 1 having good thermal conductivity, such as 5S41.5LIS.
It is made of a metal such as 31G, Cu, or Ni, or a ceramic such as silicon carbide. The helical element 1 and the inner wall of the tube are joined by brazing and held together.

A heat exchanger A equipped with this spiral element 1 is shown in FIG. 1-1. In the figure, 2 is an inner tube, and 3 is an outer tube. This example shows an example including four inner tubes 2.

In the heat exchanger A having such a configuration, when the heat exchange liquid is allowed to flow in the direction of the arrow, it is divided into two channels, and in each channel, one divided liquid is distributed to each unit element 1a...
・While moving in a spiral manner.

In addition, each unit element 1a moves in the longitudinal direction while being reversely twisted.

[test] (1) Purpose The performance of the heat exchanger of this example will be confirmed.

As a comparative example, a heat exchanger equipped with a conventional standard element (FIG. IB) was used. For reference, an empty tube (Figure I
The heat exchanger C) was also investigated.

(2) Test equipment and test method The heat exchange flow used in the test is shown in Figure 1-2.

In FIG. 1-2, rFIJ indicates a flow rate indicator, "P" indicates pressure, rP, J indicates steam pressure, and rT I Cl indicates a temperature indicator regulator. Table 1 shows the specifications of the heat exchanger. The total length (L) of each spiral element is 810m.
It was set as m.

As for the samples, water was used as the low viscosity liquid, and acid saccharified starch syrup (Sansira Rough 85) manufactured by Nippon Konstarch ■ was used as the high viscosity liquid, and the concentration was adjusted to 75%. (Physical property values are listed in Table 2) Measurement of pressure loss, heating test with steam, and cooling test with tap water were conducted.

(3) Test results (3-1) Pressure loss due to low viscosity liquid Figure 4 shows the pressure drop test results using tap water.

In the case of the example, the pressure loss is smaller than that of the comparative example, and the structure has high fluidity.

(3-2) Heating test using low viscosity liquid Figure 5 shows the results of a heating test on tap water using steam. j□ is given by equation (2) (Note 1). In the case of a low viscosity liquid such as tap water, regarding the examples and comparative examples,
It can be seen that there is no noticeable difference in thermal efficiency.

(3-3) Pressure loss due to high viscosity liquid Figure 61 Figure 7 shows the measurement results of viscosity vs. shear rate and viscosity vs. temperature of starch syrup adjusted to 75%. In this test, the range of shear rate was N-40 to 20O8-1, and it can be seen that the influence on viscosity in this range is small, but the influence of temperature is large.

FIG. 8 shows the pressure loss test results using starch syrup. Similar pressure drop results were obtained for high viscosity fluids such as starch syrup as in the case of tap water.

FIG. 9 shows a comparison between the pressure loss test results of the comparative example and the 7 estimated values. The estimated value is based on formula (3) (Note 1).The viscosity obtained by a rotational viscometer is a smaller value than the value estimated from the actual pressure loss.

The ratio is approximately 0.60. Hereafter, this viscosity will be used to organize the Reynolds number.

(3-4) Heating test using high viscosity liquid Figure 10 shows the results of a heating test using steam using starch syrup. The tube inside heat transfer coefficient hi is given by equation (I) (Note 1) and is set to φ-1,1. In the case of the example, as in the case of the comparative example, it is proportional to Re to the 1/3 power, and the coefficient A is 1.85 in the case of the comparative example. In the case of the example, 1.28 was obtained. It was found that the comparative example had slightly better thermal efficiency.

(3-5) Cooling test with high viscosity liquid Figure II shows the results of a cooling test using tap water.

In the comparative example, results similar to those obtained by heating were obtained. In the example, lower thermal efficiency was obtained at A-0,85 than in the case of heating.

(Leaving space below) Table 1 Table 2 D Estimated Value - Japan Cornstarch ■Technical Service 1 Data @ Subscripts 0 and 1 are the outside of the tube and the inside of the tube, respectively. In addition, r in the water-heating example. - “Let it be 1-o.

(4>Results (4-1) Pressure loss Regarding pressure loss, the following results were obtained.

(i) Low viscosity liquid (water) Re>104ΔP (example)/ΔP (comparative example) -0,40 to 0,45 (11) High viscosity liquid (water syrup) Re<10ΔP (example) no ΔP
(Comparative example) -0.70 to 0.75 (4-2) Heat exchange efficiency [jHko (Note 2) The following results were obtained regarding heat exchange efficiency.

(1) Low viscosity liquid (water) - steam heating Re>103j
H (Example) / j + (Comparative example) ζ 1.001) High viscosity liquid (water syrup) Re < 10 Steam heating jH (Example) / jH (Comparative example) ζ 0.70 Cooling jH (Example) / j
) l (Comparative example) ζ0゜50 (5) Consideration Regarding pressure loss, the heat exchanger of the example has a pressure loss of 0.75 or less compared to the comparative example, especially 0.45 or less in the case of low viscosity liquid. .

In the case of a steam heating system for a low viscosity fluid such as water, the heat exchanger of the example can obtain heat exchange efficiency equivalent to that of the comparative example. Even in the case of high viscosity fluid, it can be used in consideration of its simple structure and low pressure loss.

(Left below) (Note 1) (1), (2), (3) formula % formula % () (2) (3) () () If the flow rate of the fluid inside the pipe is W < kg/h), the heat The exchange rate Q (kcal/h) is Q-W-C・Δt (C: specific heat) (■) Based on the saturated steam table, the enthalpy h (kcal/h) is calculated from the secondary pressure of steam.
cal/kg) and check the steam flow rate W' (kg/kg).
h) is obtained from the following formula.

W'-Q/h (I
II) Also, the overall heat transfer coefficient U (kcal/r
r?・h・℃).

U-Q/A・ΔtIIl (Δt; logarithmic average temperature difference) (■
) Calculate hl from equation (1). Furthermore, from formula 2)
Find H. However. is calculated using a calculation formula.

(Cooling) The cooling water flow ffiW (kg/h) is actually measured, and hl is determined in the same manner as in the case of steam heating.

(Margin below)

[Brief explanation of drawings]

Figures IA, B, and C are side sectional views showing the structure of the tube body (inner tube), and 2 Figure IA is related to the example 1 Figure IB is related to the comparative example 2 Figure IC is not equipped with an element Items related to simple empty pipes. FIG. 1-1 is a side sectional view showing the heat exchanger of the example and its CC sectional view (the same applies to the comparative example except for the element). Figure 1-2 shows the heat exchange flow used in the test. Figure 2.3 is a graph showing the characteristics (specific gravity, specific heat) of starch syrup as a high viscosity liquid. FIG. 4 is a graph showing the results of pressure loss due to low viscosity liquid. FIG. 5 is a graph showing the results of a heating test using a low viscosity liquid. Figure 6.7 is a graph showing the relationship between viscosity vs. shear rate and viscosity vs. temperature for starch syrup as a high viscosity liquid. 8 and 9 are graphs showing the results of pressure loss due to high viscosity liquid. 10 is a graph showing the results of a heating test using a high viscosity liquid. FIG. 11 is a graph showing the results of a cooling test using a high viscosity liquid. respectively. 1... Helical element 1a... Unit element 2... Inner tube 3... Outer tube Figure 1A Figure 1B

Claims (4)

[Claims] (1) A helical element that extends in the longitudinal direction in the pipe, the helical element is made up of a plurality of unit elements each having a twist angle of 180° connected at a connection angle of 0°, and adjacent unit elements are twisted in the opposite direction. A heat exchange tube body characterized by: (2) Consisting of an outer tube and one or more inner tubes disposed with a gap within the outer tube, comprising a helical element extending in the longitudinal direction within the inner tube, the helical element having a twist angle of 180°. A plurality of unit elements are connected consecutively at a connection angle of 0°, and adjacent unit elements are twisted in opposite directions. A heat exchanger characterized by: (3) The tube body or heat exchanger according to claim 1 or 2, wherein the heat exchange medium is a low viscosity liquid with Re>10^4 (Re: Reynolds number). (4) The tube body or heat exchanger according to claim 1 or 2, wherein the helical element is joined to the inner wall of the tube by brazing.